title: Iron transport in Francisella in the absence of a recognizable TonB protein still requires energy generated by the proton motive force.
abstract: The mechanism of iron transport in Francisella is still a puzzle since none of the sequenced Francisella strains appears to encode a TonB protein, the energy transducer of the proton motive force necessary to act on the bacterial outer membrane siderophore receptor to allow the internalization of iron. In this work we demonstrate using kinetic experiments of radioactive Fe(3+) utilization, that iron uptake in Francisella novicida, although with no recognizable TonB protein, is indeed dependent on energy generated by the proton motive force. Moreover, mutants of a predicted outer membrane receptor still transport iron and are sensitive to the iron dependent antimicrobial compound streptonigrin. Our studies suggest that alternative pathways to internalize iron might exist in Francisella.
authors.affiliation: Department of Molecular Microbiology and Immunology, School of Medicine, Oregon Health and Science University, Portland, OR, USA. crosal@ohsu.edu
authors.forename: Lidia M
authors.initials: LM
authors.lastname: Crosa
authors.forename: Jorge H
authors.initials: JH
authors.lastname: Crosa
authors.forename: Fred
authors.initials: F
authors.lastname: Heffron
mesh_terms: D000595:Amino Acid Sequence; D018407:Bacterial Physiological Phenomena; D001426:Bacterial Proteins / Q000378:metabolism*; D001681:Biological Assay; D005290:Ferric Compounds / Q000737:chemistry; D005603:Francisella / Q000378:metabolism*; D007501:Iron / Q000737:chemistry / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D008954:Models, Biological; D008969:Molecular Sequence Data; D005810:Multigene Family; D009154:Mutation; D011522:Protons; D017262:Siderophores / Q000737:chemistry; D013308:Streptonigrin / Q000737:chemistry; D013997:Time Factors
chemical_list: D001426:Bacterial Proteins; D005290:Ferric Compounds; D008565:Membrane Proteins; D011522:Protons; D017262:Siderophores; C057616:tonB protein, Bacteria; C087496:rhizoferrin; D013308:Streptonigrin; D007501:Iron